Mass replace names in vertex groups
The list of vertex groups can be found in the object properties, we just need to search for the names we want and rename them.

You could fill in name_list from the start or just add one or two names as you find them and re-run the script. This is set to rename vertex groups in the active object.

import bpy

name_list = [
    # old name - new name
    ['lowerarm_L','forearm.L'],
    ['lowerarm_R','forearm.R'],
    ['upperarm_L','upper_arm.L'],
    ['upperarm_R','upper_arm.R'],
]

v_groups = bpy.context.active_object.vertex_groups
for n in name_list:
    if n[0] in v_groups:
        v_groups[n[0]].name = n[1]


Note that matching names this way is case-sensitive, for an insensitive match use -

v_groups = bpy.context.active_object.vertex_groups
for n in name_list:
    for vn in v_groups:
        if vn.name.lower() == n[0].lower():
            vn.name = n[1]